What Does Octane Rating Mean?

Octane rating

An octane rating determines what kind of gas you need to put in your car. Anytime you pull into a gas station, you will see three different yellow buttons with black numbers on them. These numbers tell you the different octane ratings of gasoline. While most vehicles can take gas with the lowest octane rating, not all do. Knowing the difference and understanding what your vehicle can take is essential to keep it running smoothly.

What Is an Octane Rating?

Octane ratings measure how heat-resistant fuel is. Gasoline needs to have a certain level of heat resistance to prevent combustion. The octane rating tells you how high pressure needs to be for the gas to spontaneously combust. The higher rated the gasoline is, the more stability it will have.

The number assigned to an octane rating is the average of the motor octane rating (MOR) and research octane number (RON).

Gas stations charge more for gasoline with higher gas octane ratings. Gas stations in the United States typically offer three gasoline levels: regular, midgrade, and premium. The lowest level of octane rating is regular gasoline, which usually carries an octane rating of 87. However, in areas with high elevation, regular gasoline may have a rating of 85 because the barometric pressure is lower. Midgrade gasoline has a rating of 89 to 90. Premium gasoline, the highest octane fuel, has a gas octane rating of 91 to 94.

Some gas companies have different names for the different grades of fuel. Regular gasoline is also known as unleaded, midgrade gasoline is super, and premium gasoline is super premium or super unleaded.

Testing for Gas Octane Ratings

For a company to determine what the octane rating is, an expensive and time-consuming test is conducted. The test is also referred to as the “engine knock test.” The test requires a standard engine and a controlled setting. The fuel is preheated and tested at 900 rpm to see when it combusts.

What if I Use the Wrong Gas Octane Rating?

The higher the octane rating, the more expensive the gasoline will be. Putting gas in your car is not a time for cutting corners because using unleaded gasoline in a car that requires super premium may cause damage over time. Using a lower gas octane rating than required could ruin your engine or the emissions control system.

Car manufacturers test for different gas octane ratings to determine what rating level will help the vehicle run efficiently. If you’re unsure about what gas you need to use, check your owners manual. The majority of vehicles can run on regular unleaded gasoline without incident.

On the contrary, using a higher gas octane rating than your vehicle needs won’t cause damage. Premium gasoline can help improve your car’s performance for heavy-duty activities like towing a trailer or other loads. Premium gasoline can also help cars run more efficiently in hot weather. In normal circumstances, however, premium gas will increase a car’s economy only very slightly. The benefits are so marginal that the extra amount you’d be paying for gas wouldn’t be worth it.

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